Add Support for TRY_CAST in PostgreSQL Dialect

Describe the bug
We are using the PostgreSQL dialect to verify SQL queries. Along with that, we support various SQL functions, and one of the functions we use is TRY_CAST. However, PostgreSQL dialect natively supports CAST but does not support TRY_CAST.

We need a way to add support for the TRY_CAST function, even though PostgreSQL itself does not have native support for this function.

Database Engine
PostgreSQL + Additional Custom Function

To Reproduce
-the SQL that be parsed: select TRY_CAST(field1 as INT) from table
-the node-sql-parser version: 5.2.0
Node Version: 20+

Expected behavior
TRY_CAST should function similarly to other databases that support it, where it tries to cast the value to the target type and returns NULL if the cast fails.

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Additional context
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